Dry sintering of latex particles in pigmented coatings. I. Influence on coating structure and properties

When a clay–latex coating, dried below the minimum film-forming temperature (MFT) of the latex, was subsequently heated above the MFT, its opacity and brightness were considerably enhanced. The improvement in optical properties was optimum in the latex content range of 20–40 parts per 100 parts of clay. The sintering of the latex particles, brought about by the thermal treatment, increased the average size of the microvoids to a diameter that is optimum for the scattering of light, without significantly affecting the total void content. Data on light-scattering coefficient, porosity, gloss, brightness, and oil permeability are discussed and compared to those of conventional coatings, i.e., of coatings dried above the MFT of the latex. Similar improvements in optical properties were obtained when coalescence of the latex particles was induced by exposure to a solvent.     

Influence of emulsifiers on particle size and particle size distribution of PVC latex synthesized by miniemulsion polymerization

We synthesized poly(vinyl chloride) (PVC) latexes via miniemulsion polymerization using a mixture of cetyl alcohol (CA) and sodium lauryl sulfate (SLS). A vinyl chloride miniemulsion is easily prepared by conventional mechanical stirring. Experimental design methods were applied to investigate the effects of composition and polymerization conditions on average particle size (APS) and particle size distribution (PSD) of the latexes produced. The APS of the latexes produced ranged from 0.4–0.7 μm. When the APS of the latex produced was above 0.7 μm, the resulting latex was highly unstable. The emulsifier ratio (CA/SLS) was the most prominent factor influencing APS and PSD.     

影响ABS树脂用EBR胶乳粒径的因素

考察了影响ABS树脂用乳液聚丁二烯橡胶（EBR）胶乳粒径的诸因素，包括初乳化剂用量、补加乳化剂用量、电解质用量、引发剂用量、初水配比及聚合温度等，得到了影响胶乳粒径各因素的线性关系。结果表明，影响EBR胶乳粒径的主要因素为初乳化剂、补加乳化剂及电解质用量，工业生产中应通过调节这些因素来实现不同EBR胶乳的生产。     

Surface treatment and characterization of functionalized latex particles and inorganic pigment particles used in the study of film formation from pigmented latex systems

The adsorption of sodium polyacrylate [NaPA] on noncarboxylated and carboxylated poly(n‐butyl methacrylate‐co‐n‐butyl acrylate) [P(BMA/BA)] latexes and ground calcium carbonate (GCC) was studied. The adsorption isotherms of NaPA on P(BMA/BA) latex surfaces showed that NaPA tended to adsorb to a greater extent onto the latex particle surfaces when the carboxyl group surface coverage of latex polymer particles is low, which indicates a repulsive interaction between the dissociated carboxyl groups and NaPA macroions. The electrophoretic mobility of cleaned model P(BMA/BA) latexes decreased with the increasing carboxyl group surface coverage at pH 10 due to the alkali‐swelling characteristics of carboxylated latexes. For GCC, used as extender pigment particles in the pigmented latex blend systems, the size of the GCC pigment particles stabilized with NaPA decreased during a sonification process and their ζ‐potential became increasingly negative with the addition of NaPA to the GCC pigment slurry. Particle size and ζ‐potential measurements showed that NaPA can stabilize GCC particles effectively, and the optimum concentration of NaPA to stabilize GCC is around 1 wt % based on solid GCC. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 398–404, 2006     

电解质对丁二烯聚合胶乳粒径的影响

通过改变电解质的用量,研究了丁二烯聚合过程中胶乳粒径的变化规律。结果表明,无电解质条件下胶乳粒子过小,产品流动性差;0．45份电解质体系聚合转化率高,反应时间短,产品流动性好;1．25份电解质体系胶乳粒径变化分2个阶段,反应时间长,生产效率低。     

Effect of sintering on surface chemistry and surface energy of pigmented latex coatings

Drying in the absence of water (sintering) of pigmented coatings made of styrene–butadiene (SB) latex and kaolin clay at different levels of pigmentation was investigated. As found from X-ray photoelectron spectroscopy, sintered coatings showed a higher SB area percent on the surface than did latex with a high glass-transition temperature (T_g) and dried at room temperature. This was a result of latex spreading at the surface. Sintering the high-T_g coatings that were dried at room temperature caused a decrease in the surface energy. Drying in the presence of water (wet coalescing) was compared to drying in the absence of water (sintering). Even though sintered coatings were more porous and had higher gloss, no significant difference was found in the SB/clay ratio at the surface or in the surface energy above the critical pigment volume concentration (CPVC). However, at and below CPVC, the sintering process yielded a higher SB content at the surface and a lower surface energy than the wet-coalescing process. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 968–975, 2001     

PBA/PMMA核壳结构乳胶粒子粒径分析

采用种子乳液聚合制备出了PBA/PMMA核壳结构乳胶粒子，研究并分析了MMA在3种不同投料方式（间歇法、半间歇法和平衡溶胀法）下粒子粒径变化情况。实验发现第二单体采用间歇法投料可获得较理想的核壳结构乳胶粒。     

聚合条件对丁苯胶乳粒径的影响

通过乳液聚合方法合成了适用于聚氯乙烯(PVC)改性甲基丙烯酸甲酯-丁二烯-苯乙烯共聚物(MBS)的种子胶乳,利用一步法工艺获得一定粒径的丁苯胶乳,研究了乳化剂加入量、加入方式,聚合温度,聚合反应时间对粒径的影响,合成了粒径在200～300nm的丁苯胶乳。     

Multistage latex particle size analysis by disc centrifuge photosedimentometry

Characterization of a heterogeneous latex polymer synthesis requires quantifying the association of successive stage compositions with the previous stage latex seed particles. A new method for performing this analysis is presented for uniform sized latex particles by use of a Joyce Loebl disc centrifuge photosedimentometer. An iterative procedure is employed to solve a problem of unknown particle density when a successive polymerization produces new latex particles. The procedure is applicable regardless of the monomer compositions of the various stages and eliminates problems encountered with electron microscopy of soft deformable latex particles.     

激光粒度仪在涂料分析测试中的应用

介绍了激光粒度仪的测试原理,讨论了两种分散方法分析测试试样时仪器参数的设置原则。并以锌粉的分析测试为例,对两种分散方法的测试结果进行了比较,提出了获得准确粒度分析结果的测试条件。     

丁苯胶乳合成中的粒径及其分布

用动态激光光散射法测定了丁二烯－苯乙烯乳液聚合的乳胶料粒子的粒径及其分布,结果表明,在反应初期平均粒径较大,粒径分布最宽,当单体转化率为６０％左右时,乳胶粒子分散度最低,说明粒径较大的液滴逐渐消失,继续聚合,乳胶粒子发生合并聚结,其平均粒径略有增长,粒径分布下降,加入电解质ＫＣｌ是增大乳胶平均粒径的有效方法。     

Role of particle size on latex deformation during film formation

The ability of latex particles to deform and coalesce to form an integral film upon drying is an important property in many latex coating applications. Many theories have been proposed to account for the origin of the deformation forces. The capillary forces which depend inversely on particle size have been accepted as important for latex deformation and film formation. The minimum film forming temperature (MFFT) has been found to be a function of the particle size of latexes and has been used as evidence that the capillary forces are responsible for film formation. In this study, the deforming force at MFFT has been determined from the moduli of water-equilibrated latex polymers. No particle size dependence was observed. The magnitude of the deforming forces was at least an order of magnitude lower than that predicted by the capillary force theory. Electron microscopy of film formed below the MFFT, a condition that corresponds to early stage film formation, showed significant deformation, indicating that at the beginning of film formation, forces of magnitude predicted by the capillary force theory are present. However, the magnitude of the forces decreases rapidly as film formation progresses. The MFFT particle size dependency can be explained by the difference in the degree of water plasticization. Evidence that latexes of different particle size were plasticized by water to different extents was determined from the T_gs of the latex emulsions. Presented at the 76th Annual Meeting of the Federation of Societies for Coalings Technology, on October 15, 1998, in New Orleans, LA. Emusion Polymers Research 1604 Building, Midland, MI 48674.     

乳液聚合中乳胶粒粒径大小及分布的影响因素

在乳液聚合中,乳胶粒的大小及分布对乳液的性能及其应用有很大的影响,同时也反映了乳液聚合反应进行的过程。本文综述了影响乳胶粒粒径大小及分布的各种因素,如聚合工艺、乳化剂、单体种类、聚合温度、引发剂等,并介绍了不同粒径乳液的性能及其应用。     

Attrition behavior of fine particles in a fluidized bed with bimodal particles: Influence of particle density and size ratio

To process the solid particulates in fluidized bed and slurry phase reactors, attrition is an inevitable consequence and is therefore one of the preliminary parameters for the catalyst design. In this paper, the mechanical degradation propensity of the zeolite catalysts (particles) was investigated in a bimodal distribution environment using a Gas Jet Attrition — ASTM standard fluidized bed test (D-5757). The experimentation was conducted in order to explore parameters affecting attrition phenomena in a bimodal fluidization. In a bimodal fluidization system, two different types of particles are co-fluidized isothermally. The air jet attrition index (AJI) showed distinct increases in the attrition rate of small particles in a bimodal fluidization environment under standard operating conditions, in comparison with single particle. A series of experiments were conducted using particles of various sizes, with large particles of different densities and sizes. Experimental results suggest that the relative density and particle size ratio have a significant influence on attrition behavior during co-fluidization. Therefore a generalized relationship has been drawn using Gwyn constants; those defined material properties of small particles. Moreover, distinct attrition incremental phenomenon was observed during co-fluidization owing to the change in collision pattern and impact, which was associated with relative particle density and size ratios.     

Influence of the particle size on the mechanical and electrochemical behaviour of micro- and nano-nickel matrix composite coatings

The aim of this work is the production and characterization of composite nickel matrix electrodeposits. Pure nickel and composite nickel matrix deposits containing either micro- or nano-particles of silicon carbide were prepared using a Watts type bath. The electrodeposition was carried out under both direct and pulse current conditions at different frequencies. With the same quantity of powder in the bath, the embedded micro-powder content is about 25–30%w while the nano-powder content is always less than 1%w. The mechanical properties of the nano-composites increases despite the low ceramic content. SEM micrographs of the microstructure and XRD-line profile analysis show that the presence of ceramic powder in both baths changes the crystallisation process leading to enhanced mechanical properties even at ceramic contents less than 1%, as in the nano-composite case. The presence of the ceramic phase and changes in the microstructure both decrease the mass loss during abrasion by up to 70% for micro-composites and 45% for nano-composites.     

The mean particle size in hindered settling of multisized particles

A Dirichlet-multinomial model is proposed for the distribution of the random vector (Y₁, Y₂,…, Y_p) in a spot sample of size n from a multicomponent mixture in an incompletely mixed state where Y_j (j = 1, 2,…, p) denotes the number of particles of component A_j. Estimates of model parameters are derived and a mixing index based on contact number is defined. Computer simulations are included to support the effectiveness of the derived model.     

Mass transfer in fluidized beds of inert particles Part II: Effect of particle size and density

The mass transfer rate in fluidized beds of inert particles (FIB) is shown to be dependent on the electrolyte flow velocity and the intensity of particle collisions with the electrode. The influence of particle size and density on the ratio of the magnitude of these two influences on the mass transfer rate in a FIB was studied. Use of particle materials of varying density in an FIB permits variation of the two effects. The influence of collision currents prevails in FIBs of low density materials, and the influence of interstitial velocity is dominant in beds of high density material. The ratio of these factors also depends on the size of particles of the same density. With smaller particle size the influence of collision currents is greater. Smoothing of mass transfer maxima in beds of particles both of small and high density is explained. The results establish a basis for the selection of FIB materials for electrochemical processes.     

Tuning the particle size and charge density of the crosslinked polystyrene particles

We report the synthesis of charged spherical colloidal particles of poly [styrene‐(co‐2‐propene sulfonic acid)] crosslinked with divinylbenzene by emulsion polymerization. The effects of concentration of both the emulsifier and initiator on the polymerization, particle size, and charge density are studied. The particle size is found to be dependent on both the emulsifier and initiator concentration and their power dependencies are different. Below critical micelle concentration (CMC), the particle size varies significantly within a small range of emulsifier concentration. In contrast, particle size decrease is not very pronounced at the heterogeneous (micellar) particle nucleation regime where the emulsifier concentration is well above of the CMC. The power dependencies of the number of particles on surfactant concentration are explained in the light of conversion–time profile of the polymerization. The surface charge density of the colloidal particles also varies with both the emulsifier and initiator concentration. Both the particle size and charge density show an inverse relation with the molecular weight of the polymer. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008